The present invention relates to a method of recording a plurality of documents each carrying an image on one side thereof on both sides of paper sheets in order of page, and an apparatus therefor.
Some modern copiers or similar image forming apparatuses are capable of recording, or copying, documents carrying images on one side thereof, i.e., one-sided documents on both sides of paper sheets in order of page. It is a common practice with this kind of image forming apparatus to use an automatic document feeder (ADF) for automatically transporting documents one by one to an illuminating section. In many cases, the last page of one-sided documents is copied first, and the first page is copied last. The problem with such a conventional two-sided copy mode is that when the number of documents is odd, the resulting copy sheet produced last and carrying the first page thereon has the other side or rear thereof left blank. Specifically, considering one set of copies, the first page (cover) or the rear thereof is left blank. To eliminate this problem, the operator may count the documents before setting them on the ADF and then input the number and odd/even information on the copier, so that the blank side may be automatically brought to the end of the set of copies. This kind of procedure, however, assigns the troublesome counting operation to the operator and, therefore, not only needs an extra period of time but also often invites miscount.
In the light of the above, before a copying operation, the ADF may be operated to circulate all the copies once to thereby automatically count them, as disclosed in, for example, Japanese Patent Publication No. 10943/1991. In this case, the above-stated control is selectively effected after the start of a copying operation, depending on whether the number of documents is odd or even. This method, however, requires the wasteful circulation of documents which does not contribute to the copying operation at all, resulting in time losses and, therefore, in inefficient copying. Moreover, the extra circulation of documents aggravates the possibility of jam, damage and contamination of the documents while accelerating the wear of constituent parts of the copier.
To omit the wasteful circulation of documents, the first page to the last page of documents may be subjected to two-sided copying in this order, as taught in, for example, Japanese Patent Publication No. 10620/1985 and Japanese Patent Laid-Open Publication No. 18743/1979. Then, whether the number of documents is odd or even should only be determined when the copying operation is proceeded to the last page. When the number of documents is odd, the paper sheet carrying the last page on one side thereof is discharged upside down without an image formed on the other side thereof. As a result, a set of two-sided copies is completed in order of page. However, this kind of procedure has various problems left unsolved when applied to a copier of the type advantageously operable with a finisher, e.g., a stapler or a puncher, i.e., a copier capable of finishing copies in sets, as will be discussed in detail later.